The present invention deals generally with the field of vehicle suspensions, and more specifically deals with an improved vehicle suspension.
While vehicle suspension systems have evolved from the leaf spring solid beam axle method of carrying the rolling wheels (by which a vehicle moves upon the road or over rough terrain) to independently sprung wheels, which provide a smoother ride for passenger or cargo, this invention enables a further improvement to prior systems.
Rather than having either a single leaf spring positioned laterally, or two leaf springs mounted longitudinally, to the vehicle chassis for solid beam axles, the most commonly used suspension system today is coil springs encircling shock absorbers arranged with independently attached wheels. With this method, a bump in the road or rough terrain will primarily affect only one wheel rather than directly affecting the other wheel, as is the case at the other end of a solid beam axle.
The independent method of wheel attachment is usually by hinged control arms (often called A-arms or wishbones, due to their shape), or by a single hinged arm and a sliding strut of the McPherson type. The independent method of vehicle suspension is fitted between the chassis and the individual wheel assemblies.
Heretofore, the coil spring/shock absorber or other springing devices, were most often attached directly to the lower of the hinged control arms at a distance of at least halfway out from the chassis. Sometimes further out, closer to the wheel assembly. While one end of the coil spring/shock absorber unit would be attached to the lower control arm, the other end of the coil/shock unit (or strut) would be attached directly to the chassis at a location higher than the wheel assembly and inboard (toward the chassis center line). The inboard inclination of the coil spring/shock absorber assembly would often be in the 40 to 45 degree from vertical range. Some racing vehicles had more extreme inclinations in the 50 to 60 degree range for their coil spring/shock unit or for the push/pull rod leading to the springing device.
As a wheel rolls over a bump, (or the outer wheel(s) move during cornering), the wheel rises in relation to the chassis, and thus the spring/shock absorber assembly is compressed. However, as the wheel assembly rises in a near vertical fashion, the coil spring/shock absorber combination is being compressed at angles from anywhere in the range of 40 to 60 degrees from vertical. This angularity results in the lack of a true direct relationship, since the springing unit does not travel in compression the same actual distance that the wheel travels. Part of the spring""s true force is spent acting sideways rather than vertically, resulting in a reduction of the spring force applied in opposition to the vertical movement of the wheel. The ratio of spring pressure to wheel travel changes throughout the wheel""s range of travel.
When installed at an angle, a spring will need to be of a higher rating (resistance to compression) since it is not acting in direct relationship to the vertical (near vertical) travel of the wheel. Obviously, the closer a spring and/or shock absorber, or the linkage, is mounted to the wheel assembly, the more efficient it will be. However, if the shock/spring unit or the linkage is inclined, there will not be a linear relationship of compression to travel. If the shock/spring unit or linkage is mounted further out on the lower control arm, it may be necessary for an even greater inclination, which would then require an even greater spring rate, resulting in a harsher ride for passenger or cargo.
It is important for the realization of the benefits of this novel solution to also realize the heretofore position of the coil spring/shock absorber in the inclined attitude, or the use of a nearer to vertical suspension strut (McPherson style), has necessitated the location of approximately half of either springing system""s physical hardware above the axle line, and more often than not, above the upper control arm (A-arm/wishbone) as well.
The required use of space above the axle line and above the upper control arm for placement of the coil/shock, strut, air suspension, hydraulic, electro-mechanical or other suspension systems within the confines of the body (coachwork) exterior, restricts the stylist""s freedom to design exterior surfaces to no lower than the highest point of the suspension assembly.
If it were possible to lower the height of the suspension assembly, stylists would be free to reduce the height of the exterior surface in that area, and therefore not only create new designs, but when applied to the forward or leading edge surfaces of a vehicle, reduce the frontal area and decrease drag (wind resistance). Such a reduction of frontal area would achieve the economy of increased fuel mileage, the capability of higher top speed with the same of amount of propulsive power or maintain the same top speed with less propulsive energy.
A preferred embodiment of the present invention provides a vehicle suspension system mounting a wheel, skid or track assembly to a vehicle chassis. The suspension system includes a control arm (such as an A arm or wishbone) having opposing first and second ends. A first end of the control arm is pivotally coupled to the wheel, skid or track assembly, and a second end of the control arm is pivotally mounted to the vehicle chassis. A first bell crank has a fulcrum mounted to the vehicle chassis adjacent to the wheel, skid or track assembly. The first bell crank has a first lever arm and a second lever arm, where the first lever arm and the second lever arm are oriented to define a substantially vertical plane. A first link member or pull rod has a first end pivotally connected to the control arm and a second end pivotally connected to the first lever arm of the first bell crank.
A second bell crank also has a fulcrum mounted to the vehicle chassis, where the second bell crank has a first lever arm and a second lever arm. A second link member has a first end pivotally connected to the second lever arm of the first bell crank and a second end pivotally connected to the first lever arm of the second bell crank. A springing assembly is coupled between the second lever arm of the second bell crank and the vehicle chassis.
In one preferred embodiment of the vehicle suspension system the second link member is mounted substantially horizontally. Also in a preferred embodiment, the first lever arm and the second lever arm of the second bell crank define a second plane and are mounted so that the second plane intersects the vertical plane of the first bell crank along a line defined through the length of said second link member.
It is a preferred object of the present invention to provide an improved apparatus and method to form a vehicle suspension.
Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.